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Ecological Intelligence / Subject

diatoms

Peer-reviewed North America

Ocean acidification may be shifting silicon availability beneath a Pacific food web

Evidence
Peer-reviewed
Geography
Tatoosh Island, Washington, Makah Tribal Nation waters
System
Coastal upwelling / diatoms / dissolved silicon

WHAT THE EVIDENCE SAYS

Two decades of coastal chemistry and plankton measurements showed strong declines in pH, soluble silicon relative to nitrogen and chlorophyll. Models controlling for river flow, upwelling indices and salinity remained consistent with silica-recycling losses associated with acidification.

WHY IT MATTERS / OUR READ

Acidification can potentially affect food webs through nutrient availability, not only the calcification of shells and coral skeletons. Testing the suspected silicon pathway elsewhere could reveal an overlooked productivity constraint.

CAVEATS / UNCERTAINTY

A single well-observed site with statistical models cannot prove pH directly caused the chlorophyll trend, nor establish comparable rates in all oceans.

SOURCE

Nature Communications — Wootton et al. (2026)
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Long-term Tatoosh Island observations link falling pH, dissolved silicon and chlorophyll.

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Peer-reviewed Asia

In Himalayan coal-drainage streams, resistant diatoms tracked a mixture of chemical stresses

Evidence
Peer-reviewed
Geography
Jaintia Hills, Meghalaya, India
System
Acid mine drainage; stream diatoms

WHAT THE EVIDENCE SAYS

Seasonal sampling compared three mine-drainage-affected streams with one comparator. Impacted waters were more acidic and carried elevated metal and ionic signals. Species including Pinnularia biceps and Eunotia exigua showed associations with particular multi-variable chemical gradients, supporting a role as potential local bioindicators.

WHY IT MATTERS / OUR READ

Water-quality surveillance should pair chemical measurements with biological responses: survival of tolerant organisms does not establish healthy stream condition.

CAVEATS / UNCERTAINTY

Only three dominant diatom taxa and four streams were analyzed. Associations cannot isolate individual metal effects or establish a widely transferable index without testing.

SOURCE

Water Science — primary stream chemistry and algal study
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Three mine-affected streams differed from a comparison stream in acidity, metals and ions; algal assemblages reflected their combined chemistry.

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Peer-reviewed Global

Abrupt acidification experiments may exaggerate the response they are trying to predict

Evidence
Peer-reviewed
Geography
Controlled marine-diatom evolution experiment
System
Marine phytoplankton

WHAT THE EVIDENCE SAYS

A long-term Chaetoceros muelleri experiment compared an abrupt CO₂ increase with a gradual rise from roughly 440 to 1,000 ppm across more than 1,100 generations. Abrupt exposure generated stronger growth, carbon-fixation and genomic responses than the gradual trajectory, which more closely represents the rate of environmental change.

WHY IT MATTERS / OUR READ

The rate at which an experimental stressor is imposed is part of the treatment. Results based on abrupt step changes can overstate particular organismal responses when the real environment changes more gradually.

CAVEATS / UNCERTAINTY

This is one marine diatom species in a long laboratory experiment. It does not show that all ocean-acidification effects are overestimated, and translation from culture responses to food webs or carbon cycling remains uncertain.

SOURCE

Nature Communications
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Over 1,100 generations, a gradual CO₂ increase produced weaker phenotypic and genomic shifts than the abrupt step-change commonly used in ocean-acidification experiments.

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